Biomaterial Database

Role of fibrinogen in complement inhibition by streptococcal M protein. 1992

R D Horstmann, and H J Sievertsen, and M Leippe, and V A Fischetti

Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.

M protein, the major virulence factor of group A streptococci, has antiopsonic activity in that it inhibits activation of the alternative complement pathway on the streptococcal surface. Two properties of M protein have been claimed to account for the inhibitory activity, namely, (i) its binding affinity for complement factor H, which is an inhibitor of alternative pathway activation, and (ii) its high binding affinity for fibrinogen. We have recently shown that fibrinogen, like M protein, inhibits alternative pathway activation by possessing binding affinity for factor H. Here we report that fibrinogen effectively competes with factor H for binding to M protein but retains its own binding affinity for factor H. The presence of fibrinogen did not significantly affect alternative pathway inhibition on the streptococcal surface.

UI	MeSH Term	Description	Entries
D010587	Phagocytosis	The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES).	Phagocytoses
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D003169	Complement Inactivator Proteins	Serum proteins that negatively regulate the cascade process of COMPLEMENT ACTIVATION. Uncontrolled complement activation and resulting cell lysis is potentially dangerous for the host. The complement system is tightly regulated by inactivators that accelerate the decay of intermediates and certain cell surface receptors.	Complement Cytolysis Inhibiting Proteins,Complement Cytolysis Inhibitor Proteins,Complement Inactivating Proteins,Serum Complement Inactivators,Complement Inactivators, Serum,Inactivating Proteins, Complement,Inactivator Proteins, Complement,Inactivators, Serum Complement,Proteins, Complement Inactivating,Proteins, Complement Inactivator
D003179	Complement C3b	The larger fragment generated from the cleavage of COMPLEMENT C3 by C3 CONVERTASE. It is a constituent of the ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb), and COMPLEMENT C5 CONVERTASES in both the classical (C4b2a3b) and the alternative (C3bBb3b) pathway. C3b participates in IMMUNE ADHERENCE REACTION and enhances PHAGOCYTOSIS. It can be inactivated (iC3b) or cleaved by various proteases to yield fragments such as COMPLEMENT C3C; COMPLEMENT C3D; C3e; C3f; and C3g.	C3b Complement,C3bi,Complement 3b,Complement Component 3b,Inactivated C3b,iC3b,C3b, Complement,C3b, Inactivated,Complement, C3b,Component 3b, Complement
D005340	Fibrinogen	Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides A and B, the proteolytic action of other enzymes yields different fibrinogen degradation products.	Coagulation Factor I,Factor I,Blood Coagulation Factor I,gamma-Fibrinogen,Factor I, Coagulation,gamma Fibrinogen
D000942	Antigens, Bacterial	Substances elaborated by bacteria that have antigenic activity.	Bacterial Antigen,Bacterial Antigens,Antigen, Bacterial
D001425	Bacterial Outer Membrane Proteins	Proteins isolated from the outer membrane of Gram-negative bacteria.	OMP Proteins,Outer Membrane Proteins, Bacterial,Outer Membrane Lipoproteins, Bacterial
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial
D013291	Streptococcus	A genus of gram-positive, coccoid bacteria whose organisms occur in pairs or chains. No endospores are produced. Many species exist as commensals or parasites on man or animals with some being highly pathogenic. A few species are saprophytes and occur in the natural environment.
D017242	Complement Factor H	An important soluble regulator of the alternative pathway of complement activation (COMPLEMENT ACTIVATION PATHWAY, ALTERNATIVE). It is a 139-kDa glycoprotein expressed by the liver and secreted into the blood. It binds to COMPLEMENT C3B and makes iC3b (inactivated complement 3b) susceptible to cleavage by COMPLEMENT FACTOR I. Complement factor H also inhibits the association of C3b with COMPLEMENT FACTOR B to form the C3bB proenzyme, and promotes the dissociation of Bb from the C3bBb complex (COMPLEMENT C3 CONVERTASE, ALTERNATIVE PATHWAY).	Factor H,Factor H, Complement